When facing an application with complex logic performed on the client, I
find that the most convenient way to test is to play by the rules when
submitting the input in the browser, allowing it to perform whatever checks
it wishes.
Simply intercept the request with a proxy and manipulate the fields in the
raw HTTP request. This is sometimes the only way to be able to intelligently
test the application as the JS code might add parameters or perform some
other critical functions that you might remove by accident when editing the
HTML.

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Ethical Hacking at the InfoSec Institute. All of our class sizes are
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with one of our expert instructors. Check out our Advanced Hacking course,
learn to write exploits and attack security infrastructure. Attend a course
taught by an expert instructor with years of in-the-field pen testing
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http://www.infosecinstitute.com/courses/ethical_hacking_training.html
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Ethical Hacking at the InfoSec Institute. All of our class sizes are
guaranteed to be 12 students or less to facilitate one-on-one interaction
with one of our expert instructors. Check out our Advanced Hacking course,
learn to write exploits and attack security infrastructure. Attend a course
taught by an expert instructor with years of in-the-field pen testing
experience in our state of the art hacking lab. Master the skills of an
Ethical Hacker to better assess the security of your organization.
http://www.infosecinstitute.com/courses/ethical_hacking_training.html
-------------------------------------------------------------------------------